A typical form of an internal-gear machine such as a pump comprises a casing with an internally toothed annular gear rotatably disposed therein, and an externally toothed pinion which is in meshing engagement with the annular gear. A filling member is disposed in the space between the annular gear and the pinion and is subdivided into two portions by a separating surface extending substantially in a peripheral direction. In a construction of that kind, as is to be found in DE-C-29 54 546, the separating surface which subdivides the filling member into the two portions has recesses which extend therefrom and which are disposed in respective mutually opposite relationship. The recesses have inclined surfaces which are in a wedge-like configuration relative to each other and which face in the same direction, namely from the pressure side of the machine to the suction side thereof. The machine further has a respective sealing roller which bears against each of the above-mentioned inclined surfaces and is loaded by a leaf spring in order thereby in operation of the machine to spread the portions of the filling member under the pressure acting on the sealing roller and thus to apply the portions of the filling member against the tips of the teeth on the pinion and the annular gear respectively. The leaf spring is operatively disposed between the sealing roller and a support surface which is disposed in the space at the separating surface, which is formed by the recesses in the filling member portions.
The leaf spring disposed in the above-mentioned separating surface space of the filling member is necessarily very small and therefore has to be produced and installed with a high degree of precision in order to apply a fairly precisely predetermined spring force to the sealing roller. This is a complicated and therefore expensive matter while nonetheless it is not possible reliably to avoid a fluctuation in the spring force applied to the sealing roller by the leaf spring, depending on where the tolerance dimensions of the leaf spring and the separating surface space defined by the recesses therein happen to occur.
For that reason in another structure, as is to be found in DE-A-43 36 966, a spring element for loading the sealing roller is fixed with a fixing portion thereof to one of the axial plates or housing walls of the machine, which bear axially against the filling member. Extending from the fixing portion of the spring element is a spring portion which is oriented in approximately parallel relationship with the axis of the machine and which bears against the sealing roller and which is suitably prestressed in that condition. That structural configuration admittedly permits production of the spring for loading the sealing roller to be easier and therefore less expensive. It will be noted however that the production and assembly expenditure of the internal-gear machine is not substantially reduced as a result because, in order to achieve a substantially reproducibly identical spring loading at the sealing roller, the bore provided for receiving the fixing portion of the spring in the housing of the machine or in the axial plate thereof must be very precisely positioned. Removal and fitting of the spring when implementing repair operations is also found to be a difficult operation.